The density of the steel and iron are similar enough that it tracks quite nicely. The smaller the initial hole, down to about half the final diameter, the easier it is to drill the hole and the easier it is to break the drill. Find a compromise that suits you and stock extra bits anyway. Any decent quality high speed split point jobbers bit works nicely. I use a step drill for the initial hole, because I found some about the right size at my local surplus yard years back for cheap and still haven't used them up, so I'm drilling the smaller size pilot hole, and a nearly finished size hole in one pass. This has proved to be a pretty ideal approach for me, as the step drill clears chips for both diameters easily and makes the biggest most accurately placed hole with the least work. I then ream to final size (third hole) with a second pass. As with drilling pinblocks, I find the final reaming pass of a slightly undersize hole makes a more controllably uniform fit. I use 5mm pins because I've found them to be adequately stiff, to present fewer spacing problems, and require the removal of a lot less iron than Baldwin's choice of 5.8mm. My choices. Everyone slays their dragons by their own methods. Ron N ***Curious - have you ever free hand drilled or do you always use a drill press? Gene
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